Absorbent fibrous products such as paper towels, facial tissues, bath tissues and other similar products, for example, are designed to include several important properties. For example, the products should have good bulk, a soft feel and should be highly absorbent. The product should preferably also have good strength and resist tearing, even while wet. Unfortunately, it is very difficult to produce a high strength fibrous product that is also soft and highly absorbent. Usually, when steps are taken to increase one property of the product, other characteristics of the product are adversely affected.
For instance, softness is typically increased by decreasing or reducing cellulosic fiber bonding within the fibrous product. Inhibiting or reducing fiber bonding, however, can adversely affect other properties, such as the strength of the fibrous web.
In other instances, softness can be enhanced by the topical addition of a softening agent to the outer surfaces of the fibrous web. The softening agent may comprise, for instance, a silicone. The silicone may be applied to the web by printing, coating or spraying. Although silicones make the fibrous webs feel softer, silicones can be relatively expensive and may lower sheet durability as measured by tensile strength and/or tensile energy absorbed.
In order to improve durability, in the past, various strength agents have been added to fibrous products. The strength agents may be added to increase the dry strength of the fibrous web or the wet strength of the fibrous web. Some strength agents are considered temporary, since they only maintain wet strength in the fibrous web for a specific length of time. Temporary wet strength agents, for instance, may add strength to bath tissues during use while not preventing the bath tissues from disintegrating when dropped in a toilet and flushed into a sewer line or septic tank.
Bonding agents have also been topically applied to fibrous products alone or in combination with creping operations. For example, one particular process that has proved to be very successful in producing paper towels and wipers is disclosed in U.S. Pat. No. 3,879,257 to Gentile, et al., which is incorporated herein by reference in a manner that is consistent herewith. In Gentile, et al., a process is disclosed in which a bonding material is applied in a fine, defined pattern to one side of a fibrous web. The web is then adhered to a heated creping surface and creped from the surface. A bonding material is applied to the opposite side of the web and the web is similarly creped. The process disclosed in Gentile, et al. produces wiper products having exceptional bulk, outstanding softness and good absorbency. The surface regions of the web also provide excellent strength, abrasion resistance, and wipe-dry properties.
Although the process and products disclosed in Gentile, et al. have provided many advances in the art of making paper wiping products, further improvements in various aspects of paper wiping products remain desired. For example, particular softening agents are still needed that can be incorporated into fibrous webs without significantly adversely impacting the absorbent capacity of the webs. A need also exists for a softening agent that can be incorporated into the web at any point during its production. For instance, a need exists for a softening agent that can be added to a pulpsheet prior to slurry formation, an aqueous suspension of fibers used to form a fibrous web, a formed fibrous web prior to drying, transferred to a web from a dryer surface, and/or to a fibrous web that has been dried.